As a duplex communication method in LTE (Long Term Evolution)/LTE-Advanced, TDD (Time Division Duplexing) has been known such that subframes used for uplink and subframes used for downlink within a radio frame are switched in accordance with a predetermined configuration ratio.
The ratio of the uplink and the downlink in the radio frame is determined in advance by operation, etc., by an operator depending on uplink and downlink traffic amounts, and it is reported to user equipment by system information.
Furthermore, in LTE/LTE-Advanced, in order to synchronize uplink signals transmitted from a plurality of units of the user equipment at a base station, timing advance control (TA control) has been introduced. The TA control is a scheme such that, the base station estimates a propagation delay of a signal transmitted from the user equipment, and assigns transmission timing of an uplink signal to the user equipment, so that the uplink signals transmitted from the plurality of units of the user equipment are synchronized.
Furthermore, in the TDD scheme, it is required to prevent an uplink signal and a downlink signal from being simultaneously transmitted at a certain time. For this reason, a non-transmission interval is established in consideration of the propagation delay between the user equipment and the base station, and the adjustment of the transmission timing of the uplink signal by the TA control. This non-transmission interval is referred to as a guard period (GP: Guard Period).